get_ppm

#!/bin/bash

set -e

measureppm() {
	# Grab ppm from our last run, but if it doesn't exist give it a sane default
	ppm=$4
	if [ "$ppm" == "" ]; then
		ppm=0
	fi

	newppm=$ppm
	lastppm=$ppm
	powergain=$3

	ppmsource=$2
	freq=$(echo "scale=0; ($ppmsource*1000000)/1" | bc -l)
	maxoffset=50000

	# Get some timestamps
	ts=`date +"%Y-%m-%d_%H-%M-%S"`
	csv=$1_ppm-$ts

	# Run measurements
	echo "$1: Measuring PPM (initial $ppm ppm) with reference freq of $ppmsource, please wait 45 seconds."
	rtl_power -d "$1" -c .1 -f $((freq-maxoffset)):$((freq+maxoffset)):64 -i 2 -g $powergain -p $ppm -e 45s ${csv}.csv > /dev/null 2>&1
	newppm=`perl findppm.pl $ppm $freq ${csv}.csv 1`
	# newppm=$((($RANDOM-$RANDOM)/1000))
	echo "$1: Found $ppmsource at $newppm ppm, updating config"
	if [ -s "$configfile" ]; then
		flock -w 1 $configfile sed -ri 's/"device": "rtl='$1'","ppm": (.*),/"device": "rtl='$1'","ppm": '$newppm',/' $configfile
	fi

	# Remove the data file
	rm ${csv}.csv
}


export configfile="./REPLACE_ME.json"

echo "Waiting for USB devices to be released..."
sleep 3

# Command format: measureppm rtlsdr-deviceid frequency gain

measureppm 00000001 774.34375 2 &
measureppm 00000002 774.34375 2 &
measureppm 00000003 472.7125 2 &

# Wait for all the above background jobs to complete
wait

echo "Waiting for USB devices to be released..."
sleep 3